github.com/prometheus/procfs v0.22.0: FS.CPUInfo

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:golang/github.com/prometheus/procfs@v0.22.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/procfs@v0.22.0
Demonstrate these symbols/APIs:
  - procfs.FS.CPUInfo

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:d0e60854d60067e7ed2089084c7cfc205aaa67cb6226ecf475a758061648a394","contract":["procfs.NewDefaultFS() returns (FS, error) where error is nil","fs.CPUInfo() returns ([]CPUInfo, error) where error is nil and len is positive","procfs.FS.CPUInfo returns an error when reading from a proc mount missing cpuinfo","fs.CPUInfo() parses CPUInfo list including ModelName and Processor ID"],"goal":"verify pkg:golang/github.com/prometheus/procfs@v0.22.0","kind":"HOW","packages":["pkg:golang/github.com/prometheus/procfs@v0.22.0"],"schemaVersion":1,"symbols":["procfs.FS.CPUInfo"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/prometheus/procfs@v0.22.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/procfs@v0.22.0","symbols":["procfs.FS.CPUInfo"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/prometheus/procfs v0.22.0

require golang.org/x/sys v0.47.0 // indirect

github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/prometheus/procfs v0.22.0 h1:6q9+/JL9IKAPbCmBrv9n5O5Ty3NKnciV5X7YGw0oics=
github.com/prometheus/procfs v0.22.0/go.mod h1:CvmFr/GVhIjIvWJZW3tgkODBQMRIf0EyWMQLHCHab58=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=

package main

import (
	"fmt"
	"os"

	"github.com/prometheus/procfs"
)

// ReadCPUInfo returns current CPU info list.
func ReadCPUInfo() ([]procfs.CPUInfo, error) {
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		return nil, fmt.Errorf("procfs access failed: %w", err)
	}
	return fs.CPUInfo()
}

func main() {
	cpus, err := ReadCPUInfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to read cpu info: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Detected %d CPUs\n", len(cpus))
	for _, cpu := range cpus {
		fmt.Printf("CPU %d: %s\n", cpu.Processor, cpu.ModelName)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/prometheus/procfs@v0.22.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/procfs@v0.22.0"
  ],
  "symbols": [
    "procfs.FS.CPUInfo"
  ]
}

package main

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/prometheus/procfs"
)

func main() {
	// 1. Verify procfs.NewDefaultFS returns a valid FS instance
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewDefaultFS failed: %v\n", err)
		os.Exit(1)
	}

	// 2. Verify fs.CPUInfo parses real /proc/cpuinfo
	cpuInfo, err := fs.CPUInfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.CPUInfo failed: %v\n", err)
		os.Exit(1)
	}
	if len(cpuInfo) == 0 {
		fmt.Fprintf(os.Stderr, "expected at least 1 CPU in CPUInfo\n")
		os.Exit(1)
	}

	// 3. Verify fs.CPUInfo fails when cpuinfo file is missing
	tmpDir, err := os.MkdirTemp("", "proctest*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "os.MkdirTemp failed: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

	mockFS, err := procfs.NewFS(tmpDir)
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewFS failed: %v\n", err)
		os.Exit(1)
	}

	_, err = mockFS.CPUInfo()
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected error when cpuinfo file is missing, got nil\n")
		os.Exit(1)
	}

	// 4. Verify mock cpuinfo parsing of ModelName and Processor ID
	mockContent := []byte("processor\t: 0\nvendor_id\t: GenuineIntel\ncpu family\t: 6\nmodel\t\t: 85\nmodel name\t: Test CPU Model\n\nprocessor\t: 1\nvendor_id\t: GenuineIntel\ncpu family\t: 6\nmodel\t\t: 85\nmodel name\t: Test CPU Model\n\n")
	if err := os.WriteFile(filepath.Join(tmpDir, "cpuinfo"), mockContent, 0644); err != nil {
		fmt.Fprintf(os.Stderr, "os.WriteFile failed: %v\n", err)
		os.Exit(1)
	}

	parsedCPUs, err := mockFS.CPUInfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "mockFS.CPUInfo failed: %v\n", err)
		os.Exit(1)
	}
	if len(parsedCPUs) != 2 {
		fmt.Fprintf(os.Stderr, "expected 2 CPUs parsed, got %d\n", len(parsedCPUs))
		os.Exit(1)
	}
	if parsedCPUs[0].ModelName != "Test CPU Model" {
		fmt.Fprintf(os.Stderr, "unexpected ModelName: %s\n", parsedCPUs[0].ModelName)
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed.")
}